Hi, I had a Jolida 502, and used nos Tung Sol 6550's and the best 12at7;'s I heard in this amp were Siemens 2 mica. If you are using the stock tubes, I think you will be able to improve the sound a lot with NOS tubes, especially in the warmth/weight department. I used a sub for a while with the Jolida, and with other amps as well, when I had Spendor sp1/2e"s. I was happy with the sound, but when I got a pair of full range Vandersteen 3a speakers, I realized how much the monitor/sub thing sucked. YMMV. I spent days and days, had test tones and a spl meter, I achieved a pretty flat response +/- 3 db from 30hz to 100hz, but not even close to the Vandersteens. I have since heard only one other system where sub integration was attempted, and IMO it was obvious there was a separate sub is in the mix, I have read that if you are going to attempt this, to get 2 subs, but for 500 bucks this may prove difficult. My James emb-1000 is now used for movies.
My advice if you decide to integrate a sub is that less is more.
My advice if you decide to integrate a sub is that less is more.